You do get a second chance in most things in life, as the United States and the Palestinian leadership are experiencing now, in the wake of the revived Palestinian-Israeli peace negotiations at Annapolis. The second chance to get things right has been triggered by the announcement earlier this week that Israel plans to build over 300 new housing units on occupied Palestinian Arab land in East Jerusalem at the Har Homa settlement - which the Arabs know as Jabal Abu Ghneim.

This is routine policy and practice for the Israeli government, which has moved several hundred thousand settlers into new colonial communities built all around Arab East Jerusalem since 1967. The new test - and opportunity - is for the Americans and Palestinians, who must take a stand on this continuing Israeli colonization and expansion.

The Palestinian-Israeli joint statement agreed at Annapolis said that the "United States will monitor and judge the fulfillment of the commitment of both sides of the "road map." Unless otherwise agreed by the parties, implementation of the future peace treaty will be subject to the implementation of the road map, as judged by the United States."

The American role of "monitor and judge" has always been implicit in various American mediation attempts, and is explicit now. Abdicating this role was a main failure of American and other external mediation in recent years, especially since the road map was launched in April 2003. A strong, impartial external mediator or facilitator is critical for success.

The US now has a second chance to get this role right - if it wishes to do so. The motives and intent of the US remain unclear vis-ˆ-vis brokering an Arab-Israeli peace accord; also unclear are its capacity and will to be impartial, and to override the powerful influence of pro-Israeli domestic forces in the US. If Washington wants to be a credible, effective monitor and judge, it can and should start with a speedy, firm position on Har Homa-Jabal Abu Ghneim.

The whole world views Israeli settlements as illegal and agrees that peace requires an Israeli withdrawal from all the lands occupied in 1967, in return for full Arab recognition of and coexistence with Israel within its 1967 borders. The US should unambiguously reject the Israeli arguments that there is a clear distinction between the occupied West Bank and Jerusalem, and state that implementation of the first phase of the road map, including freezing settlements, does indeed apply to Jerusalem.

We need to hear from the monitor and judge on whether Jerusalem is part of those lands occupied in 1967 referred to in UN resolutions as having to be returned to Arab sovereignty; and that land is subject to the settlement freeze required in the road map and Annapolis. How the US responds will reveal if the Annapolis process has any credibility. If the US remains ambiguous and betrays its role as monitor and judge, the integrity of the whole negotiating process will collapse.

The Palestinians for their part also face a profound new test here. Their initial reaction was typically lame. Palestinian negotiator Saeb Erakat sent an urgent message to US Secretary of State Condoleezza Rice, asking her to block the new construction. He wrote: "This is undermining Annapolis. Israel's ever-expanding settlement enterprise in the occupied Palestinian territory poses the single greatest threat to the establishment of an independent, viable and contiguous Palestinian state, and hence, to a just and lasting peace between Israelis and Palestinians."

Anyone who thinks that an appeal to Rice, the US government or the world's conscience is going to achieve anything is dreaming, because this approach has repeatedly failed. The Palestinian government has allowed itself to become a small element in the US-led global "war on terror" (in the form of Fatah's political battle with Hamas), and is deeply reliant on American money, arms and hand-holding. Washington does not respect the Palestinian government, and will not respond to yet another Palestinian letter of complaint or appeal to action.

At the start of the Oslo process in 1993, the Palestinian leadership made the mistake of leaving big issues to a later date, including settlements, refugees and Jerusalem. If the Palestinian negotiators are not total fools or total American stooges, they must quickly take a firm position on the two related issues that converge here: Washington's new role as monitor and judge and Israel's expansion of Har Homa-Jabal Abu Ghneim.

Palestinians should have a strong, clear response in case the US drops the ball on its judge and monitor role, and remains ambiguous on Israeli settlements. If the US and Israel do not freeze settlement expansion, the Palestinians must respond in a more decisive manner than they have done since 1993. Or have we learned nothing from Oslo's painful failures?